1. Field of the Invention
The present invention relates to a method of checking sprocket attachment in attaching a driven sprocket for an oil pump drive to an oil pump, for example, in a transmission and a sensor jig used for the same.
2. Description of the Prior Art
In a recent transmission for a vehicle an oil pump is located in a position at a distance from a main shaft of the transmission, and a chain is wound between a drive sprocket provided on the main shaft side and a driven sprocket mounted to the oil pump to transmit rotation from the main shaft to the oil pump, thereby driving the oil pump.
The oil pump has its rotation shaft connected to the driven sprocket, as well as supports the driven sprocket through a bearing.
Namely a pump cover 31 forming a body of an oil pump 30, as shown in FIG. 4, surrounds a rotation shaft 32 leaving a space of a predetermined distance and is provided with a cylindrical portion 34 extending along the rotation shaft 32. A driven sprocket 40 is provided in the central part with a boss portion 44 extending toward the oil pump 30, and a spline hole 45 passing through the boss portion 44.
The rotation shaft 32 also has a spline formed in a front end thereof. The boss portion 44 of the driven sprocket 40 is in spline engagement with the rotation shaft 32.
A ball bearing 50 is press-fitted onto an outer periphery of the boss portion 44. The ball bearing 50 is inserted into a bearing receiving portion 36 of the cylindrical portion 34 simultaneously when the boss portion 44 is inserted onto an outer periphery of the rotation shaft 32.
FIG. 5 is an enlarged view showing the cylindrical portion 34 viewed in the axial direction. A ring groove 37 is formed in the bearing receiving portion 36 of the cylindrical portion 34. A snap ring 39 is fitted in the ring groove 37 in advance before the ball bearing 50 is inserted into a bearing receiving portion 36. Namely, a notch portion 35 is formed in a part of the circumferential direction of the cylindrical portion 34. The snap ring 39 is fitted into the ring groove 37, by holding grips at both ends of the snap ring 39 within the notch portion 35 so as to make the grips closer with each other, and thereby reducing a diameter of the snap ring 39.
The snap ring 39 fitted in the ring groove 37, as shown in FIG. 5, is arranged in such a way that a part in the inner side of the snap ring 39 in its free state is exposed from a wall surface of the bearing receiving portion 36.
In assembling, before inserting the driven sprocket 40 into the bearing receiving portion 36, the grips of the snap ring 39 are made apart away from each other, so that the snap ring 39 is concealed inside the ring groove 37 once. The driven sprocket 40 is inserted into the bearing receiving portion 36 with the snap ring 39 concealed inside the ring groove 37 and is pushed in to a predetermined attachment position. Thereby, a ring groove 52 formed on an outer periphery of an outer lace 51 of the ball bearing 50 is in alignment with the ring groove 37 of the bearing receiving portion 36 and then, the snap ring 39 is restored back to a free state and is fitted partially into the ring groove 52 of the outer periphery of the outer lace 51, so that the snap ring 39 lies across both of the ring grooves 37 and 52.
In a case where a chamfering portion 54 is provided in an outer periphery corner of the outer lace 51 of the ball bearing 50, even if the grips of the snap ring 39 are not kept away from each other by hand, the snap ring 39 are pressed and expanded by the chamfering portion 54 when the ball bearing 50 enters into the bearing receiving portion 36 of the cylindrical portion 34. With the construction stated above the ball bearing 50 is prevented from being coming out of the cylindrical portion 34, thus the driven sprocket 40 is attached to the oil pump 30 without falling out of the rotation shaft 32.
A similar attachment construction is disclosed in Japanese Patent Laid-open Publication No. 2003-301929.
Conventionally, after the boss portion 44 of the driven sprocket 40 is inserted and pushed onto the rotation shaft 32, a worker has to lift the driven sprocket 40 by hand and check whether or not the snap ring 39 is engaged to the ring groove 52 of the ball bearing 50 and therefore the driven sprocket 40 does not come out of the cylindrical portion 34, to make sure that the driven sprocket 40 was attached in a normal position in relation to the oil pump 30.
According to this method, however, despite of no engagement of the snap ring 39 to the ring groove 52 of the ball bearing 50, there is a case where snap ring 39 looks as if it is engaged to the groove 52, due to resistance such as friction between the bearing receiving portion 36 of the cylindrical portion 34 and the ball bearing 50. This makes it difficult to have an accurate determination.
This problem is not limited to the case of attaching a driven sprocket to an oil pump, but occurs generally in sprocket attachment.